When traveling by automobile at night, it is often difficult to see the markings which outline the different lanes of a road, and is therefore difficult to assure against encroachment upon a lane or portion of the road utilized by another vehicle. To overcome this problem, lane markings may be formed with reflective paint, or be provided with reflective markers, in order to reflect light from a vehicle's headlights back to the driver of the vehicle and thereby render the lanes more readily visible.
Such reflective paints and markers are very helpful in enabling the driver of a vehicle to see the lanes ahead of him, but are of no assistance at all in viewing the lanes behind, or in determining the particular lane in which a vehicle coming up from behind is traveling. Consequently, a driver attempting to enter a freeway, or attempting to change lanes, may be forced by the limitations of time to make the desired change without full knowledge of whether the lane into which he is moving is already occupied by another vehicle approaching from behind. If the driver's appraisal of the situation is wrong, a serious accident may result.